This invention relates to the field of image scaling. In particular, the invention relates to image scaling for images including low resolution text.
There are multiple situations in which modern day applications attempt to increase the resolution of older applications in order to allow them to run effectively on newer monitors. One such example would a video game emulator. The scaling process used to increase the resolution of images works well for most cases. However, when it comes to scaling low resolution text, the most effective algorithms for dealing with images often leave the text unreadable.
To exacerbate further, current emulators only offer the ability to apply pixel scaling to all of the screen or nothing at all. The same is true of all real-time post-processing algorithms for image re-sampling.
Some algorithms which produce readable text do exist, but such algorithms are very computationally expensive and cannot be performed in real time.
The reason that text does become blurry when scaled up, is that good quality image scaling relies on creating blending (akin to anti-aliasing methods) of the new pixels that are added between existing pixels. When this is applied to low resolution text, the resulting characters become blurry and unreadable.
In a standard pixel scaling algorithm, the newly formed pixels' color values are pulled towards those of their neighbors. It is clear that applying this algorithm multiple times to a very simple image that requires hard edges, such as a letter, could cause that image to distort and become unrecognizable.